#include <bits/stdc++.h>
using namespace std;
 
#define fi first
#define se second
#define pb push_back
using vi = vector <int>;
using ll = long long;
using pii = pair <int, int>;
//~ const ll mod = 998244353;
const ll mod = 1e9 + 7;
ll qpow(ll a, ll b, ll m = mod) { ll r = 1, t = a;
	for(; b; b /= 2) { if(b & 1) r = r * t % m; t = t * t % m; } return r; }

const int N = 1e3 + 11;

ll a[N];
ll f[N][2];

void upd(ll &a, ll b) {
	if(a < b) a = b;
}

const ll inf = 1e18;

int main() {
	ios :: sync_with_stdio(false);
	
	int n, m; cin >> n >> m;
	for(int i = 1; i <= n; i ++)
		for(int j = 1; j <= m; j ++) {
			ll x; cin >> x;
			a[i] += x;
		}
	
	for(int i = 0; i < N; i ++)
		for(int j : {0, 1})
			f[i][j] = -inf;
	
	f[0][0] = 0;
	for(int i = 1; i <= n; i ++) {
		upd(f[i][0], f[i - 1][0]);
		upd(f[i][1], f[i - 1][1]);
		
		upd(f[i][1], f[i - 1][0] + a[i]);
		upd(f[i][0], f[i - 1][1] - a[i]);
	}
	
	cout << max(f[n][0], f[n][1]) << '\n';
}